Device for a tool spindle

ABSTRACT

Arrangement for a tool spindle with a pulling rod ( 3 ) axially displaceable in the spindle axle ( 1 ) for firmly attaching a tool at the spindle of the tool whereby the end of the pulling rod ( 3 ) that is opposite to the tool is accommodated in a stationary unit ( 4 ), the rotating part ( 1, 3 ) is provided with a piston ( 11 ) movably displaceable in a cylinder chamber ( 13 ) arranged in the spindle axle ( 1 ), the pulling rod ( 3 ) has at least one first axial bore ( 12   a ) opening into the cylinder chamber on one side of the piston ( 11 ) and at least one second ( 12   b ) axial bore opening into the cylinder chamber on the other side of the piston ( 11 ), the stationary unit ( 4 ) is provided with an inlet ( 16 ) in communication with the first bore ( 12   a ) and an inlet ( 14 ) in communication with the second bore ( 12    b ). The bores ( 12   a,    12   b ) can be put under pressure or respectively relieved of pressure via inlet ( 16, 14 ) from a fluid for displacing the piston ( 11 ) in one of the directions depending on the desired displacement of the piston ( 11 ) and thereby the pulling rod ( 3 ) from a releasing to an attaching position and back again. Gap sealings that separate the rotating part ( 1, 3 ) from the stationary unit ( 4 ) are arranged on either side of the respective inlet ( 14, 16 ) thereby forming a dynamic bearing during the rotation of the rotating part due to the leakage of the fluid through the gap sealings.

BACKGROUND OF THE INVENTION

The present invention relates to a wholly new tool spindle which hasbuilt-in multiple functions to simplify and assure the function of thespindle of the tool even at very high speeds of rotation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the form of exampleswith reference to the drawings.

FIGS. 1-4 show schematically examples of the tool spindle according tothe invention, whereby the spindle, due to its rotational symmetry, isonly shown as half a cross-section;

FIG. 5 shows another design of the invention in section;

FIGS. 6 and 7 shows cross-sections through the spindle axle is alonglines VI and VII in FIG. 4; and

FIG. 8 shows schematically the supply unit connected to the spindleaccording to the invention.

GENERAL DESCRIPTION OF THE TOOL SPINDLE ACCORDING TO THE INVENTION

The rotating spindle axle is designated by the reference numeral 1 andin the example shown in FIG. 1 is supported on two ball-bearings,indicated by the reference numeral 2, or alternatively on two fluidbearings 24 (FIG. 5). An axially displaceable pulling rod 3 extends inthe center of the spindle axle 1. In a per se known manner and not shownin detail here, a tool (not shown) can be attached firmly at the spindleaxle 1 by being attached to the pulling rod 3 that is axiallydisplaceable in the spindle axle 1. At the opposite end of the spindleaxle 1 to the tool, the pulling rod 3 extends into a unit 4 that isstationary in relation to the rotation of the spindle axle 1.

Cooling of the Tool

A connection for a cooling agent, indicated by the reference numeral 5,to which a tube or hose is connected through which a cooling agent, forexample, an emulsion is pumped under pressure through a central bore 6in the pulling rod 3 is arranged centrally at the stationary unit 4. Thecooling agent exits the pulling rod 3 at the connection to the tool tocool the bits of the tool in a manner that is well known. The coolant issupplied, as stated, under pressure, which is why the coolant (fluid)will leak in the gap between the stationary unit 4 and the rotatablepulling rod 3 from the area with the fluid under pressure—the areabefore the inlet of the bore 6—to a first outlet 8, which has a lowerpressure than the pressure of the supplied coolant. This gap, in forminga gap sealing, creates a pressure drop that constitutes a sealingfunction. As the gap is small, only an insignificant part of the totalflow of the coolant will pass through the gap. During the rotation ofthe pulling rod 3, the fluid in the gap will act as a dynamic fluidbearing and form a radially stabilizing force on the rotating pullingrod 3. The fluid will also conduct away the heat of friction that isformed in the dynamic fluid bearing. In order that the fluid, when itreaches the outlet 8, shall not find a way in the gap along the pullingrod 3 and the stationary part 4, a gas, for example air (blocking air)is pressed through an inlet 7 distributed in a radial plane in thestationary unit 4, which results in that even this gas (air) finds a wayin the gap towards the area with the lower pressure and thus against theleakage of fluid and towards the outlet 8, whereby the gas and the fluidthat reach the area at the outlet 8 exit the stationary part 4 throughthis via a system of channels (not shown). In this context, it should bepointed out that inlet 7 and each and every one of the other openingsincluded in the tool spindle described, are delimited axially on everyside by means of gap sealings.

Such a gap sealing brings about:

1. A sealing function that works at high speeds of rotation without wearof the component parts;

2. A dynamic bearing of the pulling rod 3 achieving a radiallystabilizing force;

3. Removal of the heat of friction that is formed in the dynamicbearing;

4. Prevention of different types of fluids mixing with one another; and

5. The leakage flow from the sealings is taken care of and returned tothe respective pump unit.

Sensor for the Axial Position of the Connecting Rod

As indicated earlier, a tool is attached firmly to the spindle with thehelp of a pulling rod 3, that, when withdrawn into the spindle, locksthe tool to it. To release the tool, the pulling rod 3 is pushed out acertain distance, whereby the tool can be removed. Significant damageand accidents can occur if the tool were to loosen from the spindle axleduring its rotation. It is therefore of utmost importance that the toolreally is tightly attached in the correct way to the spindle axle, whichhitherto has been difficult to establish.

With the present invention, such as that shown in FIG. 2, it is possibleto determine the axial position of the pulling rod 3 and thus alsoconfirm if the tool is correctly attached to the spindle axle or not.For this purpose, unit 4 is equipped with a spool 9 into whose openingthe end of the pulling rod 3 that is currently in unit 4 extends. Thespool 9, which is stationary in relation to the axial displacement ofthe pulling rod 3, will generate different current flow depending on theaxial position of the pulling rod in the spool 9. Depending on that theaxial position of the pulling rod in the spool 9, this, with thisbelonging and due to the position, specific current flow makes itpossible to determine with sufficient precision the axial position ofthe pulling rod and thereby establish limits for when the tool can bereplaced, respectively when the tool is correctly attached to thespindle axis and can be utilized. To reduce the sensitivity todisturbances due to the influence of the surrounding, the signalscarrying the information about the position of the pulling rod 3 are ledin optical fibers to a unit outside of the spindle, for example, acomputer or other control equipment, for example in the case that theactual data unit is situated in the spindle axle 1, for transformationto accessible information with the aid of per se known technology. Inthis context, it should be realized that spool 9 can in principlesurround pulling rod 3 at any location, as long as the pulling rod atthis location has a significant change of material. Within the scope ofthe invention, it is, of course, possible to use more than one spool 9.

Hydraulic Attachment and Removal of the Tool at the Spindle

FIG. 1 shows a tool spindle 1 from which it is evident that the pullingrod 3 is provided and integrated with a piston 11. In addition to thecentral bore 6, the pulling rod 3 also has bores 12 a, b, c (FIGS. 1-3)distributed around the center. The piston 11 is displaceable in acylinder chamber 13 that is accommodated in the spindle axle 1. In theposition shown in FIG. 3, the pulling rod 3 is withdrawn in the spindleaxle 1, thereby firmly holding the tool (not shown). To remove the toolin this position, hydraulic fluid is supplied under pressure through aninlet 16 at unit 4 and led into at least one first bore 12 a of thepulling rod 3, which opens adjacent to the inlet 16. The gas underpressure, supplied through inlet 7, as previously discussed, seeks apassage through a gap sealing also towards the left (as seen in theFigures) and out through an outlet 8′. By means of this outlet 8′ andthe gap sealing to the left of this, the area pressurized via inlet 16is limited as the fluid together with the gas (blocking air) exit unit 4via outlet 8′. The hydraulic fluid is led via the bore 12 a into thecylinder chamber 13 on the right-hand side of piston 11 (according toFIG. 1) and forces the piston 11 to the left. The pulling rod 3 willthus be displaced to the left, allowing the removal of the tool.

At least one second bore 12 b, which is not the same as previously namedin connection with opening 16 and which is sealed off at the endadjacent to opening 16 (FIG. 2), is provided with one or more openings14′ distributed peripherally in a radial plane and always located incommunication with an inlet 14 of unit 4 that is divided in a radialplane and axially separated from inlet 16 by a gap sealing 14″.Hydraulic fluid under pressure is supplied to the inlet 14 (wherebyinlet 16 naturally is not under pressure) and is led via the second bore12 b into the cylinder chamber 13 on the left-hand side of piston 11(according to FIG. 2) forcing the piston 11 to the right, therebydisplacing the pulling rod to the right for tightening the tool. Thepulling rod 3 is held in this position by the pressurized hydraulicfluid continuously acting on the left-hand side of the piston. As hasbeen previously mentioned in connection with the coolant liquid, thehydraulic liquid will also leak in the gap sealings between unit 4 andthe pulling rod 3 both to the right and to the left when seen in thefigure. The pressurized fluid provided through inlet 14 is restricted toits left (FIG. 2) by a gap sealing as well as an outlet 18 or a channelwith atmospheric pressure and to the right of the gap sealing by the gapsealing plus the inlet 16, which as already mentioned is now not underpressure. Pressurized air (blocking air) is also provided through aninlet 17 of unit 4 that is divided in a radial plane, which alsoprevents further leakage of hydraulic fluid to the left (in the figure)and that together with the leaking hydraulic fluid, exits unit 4 viaoutlet 18. To reduce or prevent leakage of pressurized air from inlet 17into the actual spindle, an outlet 19 with a lower pressure (atmosphericpressure) is arranged to the left of inlet 17.

Bore 12 a is open at the inlet 17 and opens to the right of piston 11,while the second bore 12 b is provided with openings 14′, is sealed atthe end adjacent to inlet 16, and opens in the cylinder chamber 13 onthe left-hand side of the piston.

In the case where fluid bearing 24 is used, see FIG. 5, and the spindlehas the design shown there, the hydraulic fluid is led under pressurethrough inlet 16 and bore 12 a to detach the tool. To attach the toolfirmly, bore 12 b is put under pressure via inlet 14 to displace piston11 to the right in the figure. In this way, the hydraulic fluid situatedto the right of the piston to be found in the bore 12 a is pressed outthrough the now depressurized inlet 16. When detaching the tool, thereverse takes place and the hydraulic fluid is pressed out through thenow depressurized inlet 14.

Cooling the Spindle at the Connection to the Rotor

The tool (not shown) is attached firmly, as stated, by the displacementof the pulling rod 3 into the tool spindle, which takes place throughthe hydraulic fluid under pressure being supplied via inlet 14 of unit 4through the second channel 12 b to the cylinder chamber 13 on the sideof the piston facing the tool, as shown in FIG. 2. Spindle axle 1 is, asshown, provided with a number of axial channels 20 a, b distributedperipherally, for example twelve channels (see FIG. 6), that open intothe cylinder chamber 13. Six channels 20 b of these twelve channels haverestrictions 21 at the connection with the cylinder chamber 13 formaintaining the pressure in the cylinder chamber 13 and for controllingthe desired amount of flow in the channels 20 a, and they are, at theopposite ends to their restrictions, connected with the other sixchannels 20 a, that are plugged tight 21′ at the cylinder chamber 13.Instead, these latter six channels 20 a open at the first bore 12 a ofthe pulling rod 3, which is inactive under these conditions, to leadaway the hydraulic fluid via the inlet 16 that is inactive while thetool is attached.

As long as the tool is attached and pressurized fluid thus acts againstthe left-hand side of the piston 11, part of the fluid will flow via therestrictions 21 through the channels 20 b in the spindle axle 1 and onback through the channels 20 a, the first bore 12 a and out via theinactive inlet 16, thereby cooling the spindle axle and the rotor 22located on the outside of the spindle axle 1, which is part of the motor32 for driving the spindle. During the detachment of the tool and thedisplacement of the pulling rod 3 to the left in the figure, thehydraulic fluid will change direction of flow and similarly cool thespindle axle 1.

Scavenging air for Blowing Clean the Tool

The pressurized air inlet 17 of unit 4, shown in FIG. 3 divided in aradial plane, with continuous pressurized air switched on during use isconnected to at least a third bore 12 c of pulling rod 3, which isplugged tight at its right-hand end of FIG. 3. When the pulling rod 3 isdisplaced to the left for detaching the tool, the pressurized air, herereferred to as scavenging air, will automatically be led out by one ormore third channels 23 in the spindle axle 1, towards the tool end ofthe spindle for blowing clean, in the accepted manner, the abuttingsurfaces of the tool cone. During attachment of a tool through thewithdrawal of the pulling rod 3, the flow of pressurized air will beautomatically broken through the tool with cone and flange sealingchannels 23.

Cooling the Spindle Axle and Thus the Rotor of a Fluid-supported ToolAxle

FIG. 5 shows the invention applied to a tool spindle 1 supported by afluid bearing schematically shown and indicated by 24. In principle,this embodiment can be said to correspond to that described previouslyin connection with ball-bearings with the difference that the channels20 b do not open in the cylinder chamber 13 but are, for example,tightly plugged at this. Coolant water is introduced via unit 4 throughan inlet 25 divided in a radial plane and into the bores 12 d of pullingrod 3, which are tightly plugged at their right-hand ends in the figure,and led via these bores 12 d into the cooling channels 26 equallydistributed around the center axis of the spindle axle 1. The ends ofthe outlets of the cooling channels 26 are provided with restrictions 27to obtain the desired level of flow in the channels 26 and draining ofcooling water from the spindle axle 1 at the channels 26. In this case,with the use of fluid bearings, the spindle is surrounded by anatmosphere under pressure, e.g. continuously supplied pressurized air,enclosed in a housing 33, i.e. air under pressure is therebycontinuously introduced in gap sealing 29′ between the pulling rod 3 andunit 4, which means that cooling water leaking in the gap is preventedfrom forcing its way out into the said gap but is instead collected inan outlet 28 for onward transport from unit 4.

Similarly, air under pressure is supplied to a gap sealing due to thepressurized housing 33 around the spindle axle 1, to prevent fluid thathas left the left-hand bearing 24 or the coolant that has passed therestrictions 27 in the spindle axis, from being forced in via this gap.The fluid is collected in space 30 to, together with the blocking air,be led out from the spindle unit via several channels 31 that also coolthe stator in the spindle. Fluid leakage from the right-hand fluidbearing is collected in channels on either side of the bearing anddrained, due to the pressure in housing 33, via lines (not shown) to theoutside of the housing, e.g. through connection to channels 31.

System of Supply

One problem with a spindle according to that described and that uses afluid (liquid, gas) as a significant means for its function is toachieve a large degree of reliable operation and ensure that the fluidmeets its intended function with the desired volume and pressure.

During disturbance to the monitoring and control systems, or malfunctionof the fluid supply to the spindle, it is necessary that the spindleaxle be stopped before the disturbance or malfunction leads to damage orbecomes a risk for the operation of the spindle.

A secure function of the described spindle can be achieved through thesupply of fluid for the respective function taking place through supplychannels that are independent of one another, especially through themost sensitive sections, for example where flexible connections arerequired.

With the aid of pressure and flow monitors, it is possible tocontinuously monitor the different functions, i.e. pressure and flow inthe respective channel, so that the values fall within the desiredlimits. It is thus possible that when the spindle does not rotate and anindicator shows that the desired value does not fall within its limits,or that the indicator shows that the monitoring units are notfunctioning, the spindle cannot be started. If the signals show that thevalue affected does not fall within the desired limits during theoperation of the spindle, or that the monitoring units are notfunctioning, the spindle is switched off. In this case, it is importantthat an emergency system is readily available to allow the spindle tocome to a standstill by itself before the supply of fluid ceases.

During disturbances in the system, it is very important that the spindlecan be stopped and that it shall thus be possible to remove the fluidfrom the locations where fluid can spread in an uncontrolled manner andcause damage in that the active control of the location of the fluidceases.

FIG. 8 shows schematically the supply unit according to the invention,designated by F, for the functional supply of the tool spindle, which asaccording to that described previously, includes the spindle axle 1 andits ball-bearings 2 respective fluid bearings plus the gap sealings thatare included.

The receiving and processing system 9F for the current flow or opticalsignals from the spool 9 at the tool spindle, with the aid of which theaxial position of the pulling rod 3 can be determined, is shown on theright in FIG. 8.

To cool the tool, a coolant fluid with a pressure of 10-140 bar is fedto the tool cooling system 5F, which consists of, when viewed in thedirection of flow, a cut-off valve 501, a check valve 502 and a pressuremonitor 503, which senses that the said pressure falls withinpredetermined limits. Coolant fluid fed to the tool spindle that haspassed gap sealing is led away and is indicated symbolically with thearrow 504.

Protective air or blocking air with a minimum pressure of 6 bar is fedto inlet 7 via a cut-off valve 701 in the blocking air pathway 7F plus apressure monitor 702, a check valve 703, an accumulator 704 and aregulator 705, the latter of which adjusts the outgoing pressure todesired pressure. The line from regulator 705 connects with at least twosupply channels 706 that are independent of one another, each having apressure monitor, and connected to inlet 7 of the tool spindle. Pressuremonitor 702 monitors that the correct pressure prevails in circuit 7F.In the accumulator 704, there is a certain amount of air accumulatedwith a pressure of 6-7 bar. If the blocking air disappears, the pressuredrop is sensed by the pressure monitor 702 and the accumulator 704 incircuit 7F is automatically connected, at the same time as a signal thatthe supply of energy for the operation of the tool spindle is to beinterrupted is emitted. The accumulator is emptied successively and hasa capacity that allows removal of fluid from locations, where it is notdesired, the whole time up to and following the stoppage of the spindle.

For cooling the spindle—rotor 22—coolant is supplied via circuit 16Fwith a pressure of, for example, 6 bar. This circuit includes, in theorder of the direction of flow, a flow monitor 161 that senses that asufficient level of flow exists in the circuit, a pressure monitor 162according to that stated earlier, a check valve 163, an accumulator 164,a regulator 165 plus a check valve 166, before this circuit connects toor feeds two supply channels 167 that are independent of one another,each having a pressure monitor and connected to the inlets 14, 16 of thetool spindle. Accumulator 164 holds a certain amount of fluid with apressure of 6-7 bar. This accumulator 164 acts in principle in the sameway as accumulator 704 in the circuit 7F and thus is responsible forthat the spindle—rotor 22—is supplied with coolant fluid for as long asthe spindle rotates. The regulator 165 adjusts the outgoing pressure tothe desired pressure, for example, 6 bar. The coolant fluid exits thespindle via channel 31 (see also FIG. 5).

The feed system 24F for supplying fluid to the fluid bearing 24 of thetool spindle is shown furthest to the left in FIG. 8. The fluid issupplied to the system with a pressure of, for example, 100 bar andflows through a pressure monitor 241, a check valve 242, and accumulator243, suitably a flow monitor 244, a check valve 245 to be then led tothe spindle via at least two supply channels 246 that are independent ofone another and include a respective pressure monitor 247. The differentcomponents have in principle a function that is equivalent to thatpreviously described in connection with system 7F and 16F. The task ofthe flow monitor 244 is to register that the correct amount offluid—flow—passes.

Hydraulic circuit 14F is arranged for adjusting the hydraulic system,for the pressure-setting of the different sides of the piston 11 forattaching or removing the tool. A branched line, to which a regulator141 and a check valve 142 is connected, is arranged after theaccumulator 243 in circuit 24F and before the flow monitor 244, afterwhich the branched line connects to a multi-way valve, a so-calledfour-two valve or cross-parallel valve 143. The regulator is adjusted toa pressure of, for example, 60 bar. The pressurized hydraulic fluid isled out via valve 143 through at least two supply channels 144 that areindependent of one another and provided with pressure monitors, and invia the inlet 14 of the tool spindle for displacing the piston 11 to theright (see FIG. 1) and attaching the tool. During this process, the line145 connected from the valve 143 to the inlet 16 of the tool spindle isnot under pressure so that the hydraulic fluid can be led away. Toremove the tool, the valve 143 is turned so that pressure is releasedfrom the connection 144 and the line 145 is pressurized. To sense thatthe line 145 has the desired pressure, a pressure monitor 146 isarranged in the line. The return of the said fluid is led away via line147.

Part of the branched line 707 connected to system 5F between check valve502 and pressure monitor 503 extends from system 7F after its regulator705 via check valve 708. Another part of the branched line 707 connectsto system 24F upstream of its supply channels 247 via a check valve 708a. Branched line 707 also connects to valve 143 of system 14F via acheck valve 709, and similarly via a check valve 710 to system 16Fdownstream of its check valve 166.

If, for example, a malfunction occurs in system 5F and the pressure inthis falls below 4 bar, for example, which is the pressure prevailing inbranched line 707, and the spindle axle stops, air from system 7F withan initial pressure of 4 bar will flow from system 7F into the bore 6 ofthe spindle axle to remove the coolant fluid from the affected parts ofthe spindle axle and to, to a certain extent, contribute to the coolingof the tool. Check valve 708 will naturally prevent the coolant fluid insystem 5F forcing its way into branched line 707.

In the equivalent way, if the pressure in system 4F falls below 4 bar,or if another fault arises and the spindle stops, air from system 7Fwill open check valve 710 and force away the fluid currently prevailingin the spindle and, to a certain extent, contribute to the cooling ofthe tool.

The equivalent applies during an unauthorized pressure drop or othermalfunction to feed system 14F via check valve 709 and valve 143, and/orfeed system 24, during malfunction, via check valve 708 a withpressurized air from system 7F to remove fluid that is not appropriatethere.

The pressure and flow monitors signal when the prevailing values lieoutside of the intended limits and cut off the supply of energy to thespindle axle.

Alternative Embodiment

The invention described here is not limited to exactly the designdescribed as the tool spindle can naturally be given anotherconstruction. For example, the spindle axle 1 can extend into and beaccommodated by the stationary part 4, whereby the gap sealings will belocated between this and the spindle axle 1. In this case, it ispossible to position the axial bores 12 a, 12 b for hydraulic fluid inthe spindle axle 1 instead of the pulling rod 3.

The pressures specified in connection with the described supply systemare appropriate but are given only as examples and can naturally varydepending on different parameters. Parts 244-247 do not apply whenball-bearings are used and instead, the system has lubricant monitoringof the ball-bearings added to it.

Similarly, it should be emphasized that the schematically indicated balland fluid bearings 2 and 24 respectively have what is a per se knownaxle bearing function, which has been omitted in order not to make thedescription and drawings more complicated than necessary.

What is claimed is:
 1. Arrangement for a tool spindle comprising: (a) aspindle axle having a cylinder chamber arranged therein; (b) a pullingrod axially rotatable and axially displaceable in the spindle axle forfirmly attaching a tool, the pulling rod provided with a piston movablydisplaceable in the cylinder chamber arranged in the spindle axle, thepulling rod has at least one first axial bore running in the pulling rodand opening into the cylinder chamber on one side of the piston and atleast one second axial bore running in the pulling rod and opening intothe cylinder chamber on the other side of the piston; (c) a stationaryunit accommodating an end of the pulling rod that is opposite to thetool, the stationary unit is provided with an inlet in communicationwith the at least one first bore and an inlet in communication with theat least one second bore, the bores can be put under pressure orrespectively relieved of pressure from a fluid via the inlets fordisplacing the piston and thereby the pulling rod from a tool releasingposition to a tool attaching position and back again, the stationaryunit and the pulling rod define gap sealings arranged on either side ofthe respective inlets thereby forming a dynamic bearing during therotation of the pulling rod in the stationary unit due to the leakage ofthe fluid through the gap sealings.
 2. Arrangement according to claim 1,wherein the inlets are arranged next to one another and, on either sideof the inlets, when viewed in an axial direction, there is respectivelyan outlet arranged in the stationary unit and communicating with one ofthe gap sealings, and each of the outlets has a pressure lower than thefluid.
 3. Arrangement according to claim 2, wherein the fluid fordisplacing the piston and thereby for positioning of the pulling rodcontinuously acts with pressure against the piston for both releasingthe tool and attaching and holding the tool during the rotation of thetool spindle.
 4. Arrangement according to claim 3, wherein the fluid isan hydraulic fluid.
 5. Arrangement according to claim 1, wherein thefluid for displacing the piston and thereby for positioning of thepulling rod continuously acts with pressure against the piston for bothreleasing the tool and attaching and holding the tool during therotation of the tool spindle.
 6. Arrangement according to claim 5,wherein the fluid is an hydraulic fluid.
 7. Arrangement according toclaim 1, wherein the fluid is an hydraulic fluid.